XPC initiation codon mutation in xeroderma pigmentosum patients with and without neurological symptoms.
Two unrelated xeroderma pigmentosum (XP) patients, with and without neurological abnormalities, respectively, had identical defects in the XPC DNA nucleotide excision repair (NER) gene. Patient XP21BE, a 27-year-old woman, had developmental delay and early onset of sensorineural hearing loss. In contrast, patient XP329BE, a 13-year-old boy, had a normal neurological examination. Both patients had marked lentiginous hyperpigmentation and multiple skin cancers at an early age. Their cultured fibroblasts showed similar hypersensitivity to killing by UV and reduced repair of DNA photoproducts. Cells from both patients had a homozygous c.2T>G mutation in the XPC gene which changed the ATG initiation codon to arginine (AGG). Both had low levels of XPC message and no detectable XPC protein on Western blotting. There was no functional XPC activity in both as revealed by the failure of localization of XPC and other NER proteins at the sites of UV-induced DNA damage in a sensitive in vivo immunofluorescence assay. XPC cDNA containing the initiation codon mutation was functionally inactive in a post-UV host cell reactivation (HCR) assay. Microsatellite markers flanking the XPC gene showed only a small region of identity ( approximately 30kBP), indicating that the patients were not closely related. Thus, the initiation codon mutation resulted in DNA repair deficiency in cells from both patients and greatly increased cancer susceptibility. The neurological abnormalities in patient XP21BE may be related to close consanguinity and simultaneous inheritance of other recessive genes or other gene modifying effects rather than the influence of XPC gene itself.
Khan
Sikandar G
SG
Basic Research Laboratory, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, United States.
Oh
Kyu-Seon
KS
Emmert
Steffen
S
Imoto
Kyoko
K
Tamura
Deborah
D
Digiovanna
John J
JJ
Shahlavi
Tala
T
Armstrong
Najealicka
N
Baker
Carl C
CC
Neuburg
Marcy
M
Zalewski
Chris
C
Brewer
Carmen
C
Wiggs
Edythe
E
Schiffmann
Raphael
R
Kraemer
Kenneth H
KH
D000293:Adolescent; D000328:Adult; D002460:Cell Line; D018387:Codon, Initiator / Q000378:metabolism*; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D018895:Microsatellite Repeats; D009154:Mutation; D009422:Nervous System Diseases / Q000209:etiology / Q000235:genetics* / Q000378:metabolism; D012878:Skin Neoplasms / Q000235:genetics / Q000378:metabolism; D014466:Ultraviolet Rays; D014983:Xeroderma Pigmentosum / Q000150:complications / Q000235:genetics* / Q000378:metabolism
D018387:Codon, Initiator; D004268:DNA-Binding Proteins; C086984:XPC protein, human